| 摘要 |
<p>The present invention provides a catalyst deterioration judgment device that can accurately perform a catalyst deterioration judgment by considering an oxygen density at downstream of an exhaust purification catalyst. The system reads outputs VO2 and VNH3 of an oxygen sensor and an ammonia sensor that are installed in downstream of an NSR catalyst when the catalyst is in an activate condition (step 104). When this read oxygen sensor output VO2 is equal to or more than a reference value a and the ammonia sensor output VNH3 is equal to or more than a reference value B, it is estimated that ammonia oxidizing reaction does not occur under existence of oxygen in the NSR catalyst. In this case, the NSR catalyst is judged to be deteriorated (step 108, 110, 114).</p> |
